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HP Forum Archive 13

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HP-67 Display: Big Trouble -> HELP!
Message #1 Posted by Albert on 24 Sept 2003, 5:29 p.m.


I've a big trouble with my HP-67 display: two days ago it began to light on several segments as a "shadow". I mean, for instance: 0.00 is shown as 8.88, but not on all segments with the same brightness. It happens on the 'almost' every 15 digits (sign digits shows "-" dull).

The machine works fine (programming, calculating and storing run OK).

Would anyone bring me the two ICs display drivers pin out? May be the three current drivers were out at the same time? Is a bastard drain resistor guilty, or a dead capacitor? Perhaps the problem is there ... I don't know, really. What can I do?

Thanks in advance,


Re: HP-67 Display: Big Trouble -> HELP!
Message #2 Posted by David Smith on 25 Sept 2003, 3:09 p.m.,
in response to message #1 by Albert

The middle segment of the HP67 display is a very weird thing. It is driven differently than the other segments because of the way the sign and exponent sign are decoded. Most of those discrete transistors on the keyboard circuit board are for doing that segment.

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